1. Field of the Invention:
The invention finds utility in the testing and certification of castings to determine in a nondestructive manner the workable qualities thereof.
2. Description of the Prior Art:
According to prior art techniques, castings were visually inspected once they had been taken out of the mold to determine the presence of cracks, inclusions, voids, and the like. A further test for voids was the grinding of the ingate, that part of the casting where the molten metal is poured into the mold, inspecting the same for pock marks which is indicative of the presence of voids and would tend to indicate their presence in the remaining portion of the casting. Certain sophisticated X-ray techniques can be employed to discover defects in the structure of the casting which includes foreign material, the present of large voids inside of the casting or unusual shapes or structure within the casting itself. However, with such techniques it is generally not possible to determine hydrogen embittlement or other undesirable characteristics that decrease the amount of plastic flow within the casting. The amount of plastic flow or ductility of the casting is important to the overall performance of the casting, if the casting is to be used in the electrical industry, where low electrical resistance at the wire terminal interface depends on the degree mechanical bond between the conductor and the terminal itself. Further, the presence of defects in the casting, such as cracks, become important when the casting is exposed to the environment, as by being left in the air in a overground installation or being buried underground within the soil itself. The presence of moisture, acids and other material, present in both the air and the ground, are able to penetrate the junction through these cracks and attack connector and the conductor itself and thus lead to the destruction of the joint. However, long prior to the actual destruction or the mechanical breaking of the joint, the electrical conductivity of the joint will be effected and the joint will become what is known as a hot contact or high resistance contact detrimental to the electrical system of which it is a part. Sampling techniques are not generally applicable to batch testing of castings, in that each casting is separate and discrete having been subjected to possibly different temperatures and pressures as the material is heated, poured, and the casting is allowed to cool.